A completely heterozygous A+ blood typed man has children with a woman who is completely heterozygous B+ blood type. How many different possible phenotypes could their children be?

Heterozygous A+ and B+ can form phenotypes such as AB+, A+, B+, O.

Explanation:

Using the punnet square, Heterozygous A+ combination with B+ can form phenotypes AB+, A+, B+, O. Below is an attachment that explains it better.

Reference: Google.

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Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.